The present invention relates to a leap year compensation circuit for a digital watch and, more particularly, to a leap year compensating circuit for a digital watch which multifunctionally uses time and date information.
Digital watches have recently been assembled in various devices. Along with time information of the digital watch, operating conditions of these devices are controlled. As an example, information such as date and time of issuance of a bill to a customer may be displayed. The digital watch has been widely utilized in a variety of applications. A one-chip wristwatch-type LSI which is directly connected to a display element is not suitable for the above applications. A simple LSI for a digital watch which combines counters is used for the above purpose. With the LSI of this type, compensation for a short month (consisting of 30 days) and a long month (consisting of 31 days) can be performed. However, it can hardly compensate for a leap year. Even if a digital watch can compensate for a leap year, setting for the leap year must be done before 11 o'clock 59 minutes and 59 seconds at midnight on February 28. If this setting is not done, leap year compensation cannot be performed and the watch advances as if for a regular year. On the other hand, if the setting for the leap year is not released, leap year compensation is continued even into regular years. In a device with the digital watch of this type, incorrect data may be printed.
Further, dates may be displayed in the dominical year (AD) or in a Japanese era, that is, "Showa" (the first year of "Showa" era corresponds to 1925 AD). Some devices display dates either in AD for export use or in the Japanese era for domestic use. However, in addition, a leap year compensation circuit has been desired for some time.